JP2005320486A - Lubricating oil composition - Google Patents

Abstract

【Task】
An object of the present invention is to provide a lubricating oil composition excellent in wear resistance and fatigue resistance for lubrication of a sliding portion such as a gear or a bearing that is subjected to a contact surface pressure of about 800 to 2000 MPa.
[Solution]
A lubricating oil composition containing 5 to 20% by volume of a compound having a viscosity at 100 ° C. of 1000 Pa · s or less under a pressure of 700 MPa or less and vitrified to 40000 Pa · s or more under a pressure of 800 MPa or more.
[Selection figure] None

Description

  The present invention relates to a lubricating oil composition suitable for lubricating a portion (for example, a bearing, a gear, etc.) having a very high contact surface pressure.

  In recent years, automotive gear oils or engine oils tend to have a low viscosity in order to improve fuel efficiency and shift operability. However, if low viscosity oil is used, on the other hand, especially on sliding surfaces (about 800 to 2000 MPa) with high contact surface pressure such as bearings and gears, the oil film thickness tends to decrease and the oil film breaks easily. Cause fatigue (pitching).

  As a lubricating oil composition with improved wear resistance and fatigue resistance, for example, Japanese Patent Application Laid-Open No. 05-230486 and Japanese Patent Publication No. 02-21434 are known. However, the grease described in Japanese Patent Application Laid-Open No. 05-230486 is effective in a sliding portion where a surface pressure of about 100 MPa is applied, and improvement in wear resistance and fatigue resistance cannot be expected in a region of about 800 to 2000 MPa. In addition, the grease described in Japanese Examined Patent Publication No. 02-21434 is effective under conditions of an extremely high surface pressure of about 8000 MPa and is not suitable for lubricating a sliding surface having a surface pressure of about 800 to 2000 MPa.

  Naphthenic compounds such as saturated cyclic hydrocarbons may be used as the lubricating oil component (for example, JP-A-63-178197, JP-A-7-133235, etc.). Naphthenic compounds are often used as base oils for traction drive fluids because of their high traction coefficient, but wear and fatigue on sliding surfaces where contact surface pressure of about 800 to 2000 MPa is applied, such as gears and bearings. The effect of is not known.

JP-A 63-178197 JP 7-133235 A

  An object of the present invention is to provide a lubricating oil composition excellent in wear resistance and fatigue resistance for lubrication of a sliding portion where a contact surface pressure of about 800 to 2000 MPa is applied, such as a gear or a bearing. To do.

  As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be obtained by using a lubricating oil composition containing a compound that is vitrified under an ultrahigh pressure of 800 MPa or more and has a viscosity at 100 ° C. of 40000 Pa · s or more. As a result, the present invention has been completed.

That is, the present invention includes the following inventions.
(1) A lubricating oil composition containing 5 to 20% by volume of a compound having a viscosity at 100 ° C. of 1000 Pa · s or less under a pressure of 700 MPa or less and vitrified to 40000 Pa · s or more under a pressure of 800 MPa or more.

(2) The lubricating oil composition according to the above (1), wherein the compound is di (C _3-8 cycloalkyl) alkane.

［式中、Ｒ^１は直鎖若しくは分岐Ｃ_１−６アルキル基が置換していてもよいＣ_１−６アルキレン基であり、Ｒ^２及びＲ^３は、独立して、直鎖若しくは分岐Ｃ_１−６アルキル基、フェニル基及びハロゲンからなる群より選択される。］
で表されるジシクロヘキシルアルカンである前記（１）記載の潤滑油組成物。 (3) The compound is of formula (I):

[Wherein, R ¹ is a C _1-6 alkylene group _optionally substituted by a linear or branched C _1-6 alkyl group, and R ² and R ³ are independently linear or branched C _{1 -6} selected from the group consisting of alkyl groups, phenyl groups and halogens. ]
The lubricating oil composition according to the above (1), which is a dicyclohexylalkane represented by the formula:

(4) The lubricating oil composition according to any one of the above (1) to (3) for sliding surface lubrication having a contact surface pressure of 800 to 2000 MPa.

(5) The lubricating oil composition according to any one of (1) to (4), which is for bearings or gears.

  According to the present invention, there is provided a lubricating oil composition having a high effect of suppressing wear and fatigue (pitting, fatigue damage, crack propagation) of a sliding portion to which a contact surface pressure of about 800 to 2000 MPa is applied, such as a gear or a bearing.

  The present invention is described in detail below.

  The lubricating oil composition of the present invention has a viscosity of 100 Pa or less at a pressure of 700 MPa or less, and is vitrified at a pressure of 1000 Pa · s or less (for example, 0.1 to 1000 Pa · s at 40 ° C. and 1 atm) and 800 MPa or more. It contains the compound which becomes 40000 Pa.s or more. The compound used in the present invention has, for example, pressure-viscosity (@ 100 ° C.) characteristics as shown in FIG. That is, the compound used in the present invention exists as a low-viscosity liquid having a 100 ° C. viscosity of 1000 Pa · s or less at a pressure of 700 MPa or less, vitrifies at a pressure of 800 MPa or more, and has a viscosity of 40000 Pa · s or more at 100 ° C. The compound is preferably 40,000 to 60,000 Pa · s). Here, “vitrification” as used in the present specification means that the lubricating oil molecules in a liquid state at low pressure (for example, 700 MPa or less) are subjected to pressure (for example, 800 MPa or more), whereby the distance between the molecules decreases. The phenomenon that a solid state (for example, an amorphous state) is caused by an increase in intermolecular force. The vitrified lubricating oil returns to the original liquid state from which pressure is unloaded.

Although it does not specifically limit as a compound which has the above pressure-viscosity characteristics, For example, the saturated hydrocarbon which has at least 2 cycloalkyl group is mentioned. Such saturated hydrocarbons include, for example, di (C _3-8 cycloalkyl) alkanes, particularly the following formula (I):

［式中、Ｒ^１は直鎖若しくは分岐Ｃ_１−６アルキル基が置換していてもよいＣ_１−６アルキレン基であり、Ｒ^２及びＲ^３は、独立して、水素、直鎖若しくは分岐Ｃ_１−６アルキル基、フェニル基及びハロゲンからなる群より選択される。］
で表されるジシクロヘキシルアルカンが好ましい。

[Wherein, R ¹ is a C _1-6 alkylene group _optionally substituted by a linear or branched C _1-6 alkyl group, and R ² and R ³ are independently hydrogen, linear or branched. Selected from the group consisting of a C _1-6 alkyl group, a phenyl group and a halogen. ]
The dicyclohexylalkane represented by these is preferable.

The C _1-6 alkyl group may be linear or branched. For example, methyl, ethyl, 1-propyl, 2-propyl, n-butyl, sec-butyl, tert-butyl, 2- Examples thereof include methylpropyl, pentyl and hexyl, and a C _1-3 alkyl group is particularly preferable.

The C _1-6 alkylene group may be linear or branched, and examples thereof include methylene, ethylene, propylene, butylene, pentylene, hexylene, and the like, and a C _1-3 alkylene group is particularly preferable.

  Examples of the halogen include fluorine, chlorine, bromine and iodine, and chlorine and bromine are particularly preferable.

  Examples of the dicyclohexylalkane that can be used in the present invention include the following compounds (wherein X is chlorine or bromine):

  The lubricating oil composition of the present invention contains 5 to 20% by volume, preferably 10 to 18% by volume, of the above compound. If the content is less than 5% by volume, vitrification becomes insufficient, a firm oil film cannot be formed on the sliding surface, and wear or fatigue may occur on the sliding surface. On the other hand, when the content exceeds 20% by volume, the low temperature viscosity of the lubricating oil composition is increased, and the low temperature startability is deteriorated.

  The base oil used in the lubricating oil composition of the present invention is not particularly limited, and any of mineral oil and synthetic oil can be used, for example, neutral oil, bright stock, hydrogen contact refined oil and catalytic dewaxing. Mineral oils such as refined oils; α-olefin oligomers such as liquid polybutene and liquid decene oligomers, and hydrocarbon-based synthetic oils such as liquid ethylene / α-olefin co-oligomers; Examples thereof include basic acid esters; polyol ester synthetic oils obtained by esterifying polyols such as trimethylolpropane, pentaerythritol and dipentaerythritol with fatty acids. These can be used alone or in combination of two or more.

  Furthermore, in order to improve the performance of the lubricating oil composition of the present invention, various commonly used additives can be used as needed. These include known lubricating oil additives such as antioxidants, metal deactivators, extreme pressure agents, antifoaming agents, viscosity index improvers, pour point depressants, cleaning dispersants, rust inhibitors and demulsifiers. Illustrated.

  As amine-based antioxidants, p, p′-dioctyl-diphenylamine (manufactured by Seiko Chemical Co., Ltd .: non-flex OD-3), p, p′-di-α-methylbenzyl-diphenylamine, Np-butylphenyl- Dialkyl-diphenylamines such as Np′-octylphenylamine; monoalkyldiphenylamines such as mono-t-butyldiphenylamine and monooctyldiphenylamine; di (2,4-diethylphenyl) amine, di (2-ethyl-4 -Bis (dialkylphenyl) amines such as nonylphenyl) amine; alkylphenyl-1-naphthylamines such as octylphenyl-1-naphthylamine, Nt-dodecylphenyl-1-naphthylamine; 1-naphthylamine, phenyl-1- Naphthylamine, phenyl-2-na Aryl-naphthylamines such as tilamine, N-hexylphenyl-2-naphthylamine, N-octylphenyl-2-naphthylamine, N, N′-diisopropyl-p-phenylenediamine, N, N′-diphenyl-p-phenylenediamine, etc. And phenothiazines such as phenothiazine (Hodogaya Chemical Co., Ltd .: Phenothiazine) and 3,7-dioctylphenothiazine.

  Examples of sulfur-based antioxidants include dialkyl sulfides such as didodecyl sulfide and dioctadecyl sulfide; Thiodipropionic acid esters; 2-mercaptobenzimidazole and the like.

  Examples of phenolic antioxidants include 2-t-butylphenol, 2-t-butyl-4-methylphenol, 2-t-butyl-5-methylphenol, 2,4-di-t-butylphenol, 2,4- Dimethyl-6-t-butylphenol, 2-t-butyl-4-methoxyphenol, 3-t-butyl-4-methoxyphenol, 2,5-di-t-butylhydroquinone (manufactured by Kawaguchi Chemical Co., Ltd .: Antage DBH), 2,6-di-t-butylphenol such as 2,6-di-t-butylphenol, 2,6-di-t-butyl-4-methylphenol, 2,6-di-t-butyl-4-ethylphenol -4-alkylphenols; 2,6-di-t-butyl- such as 2,6-di-t-butyl-4-methoxyphenol and 2,6-di-t-butyl-4-ethoxyphenol -Alkoxyphenols; 3,5-di-t-butyl-4-hydroxybenzylmercapto-octyl acetate, n-octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate (Yoshitomi Pharmaceutical) Manufactured by Yoshinox SS), n-dodecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, 2′-ethylhexyl-3- (3,5-di-t-butyl-4) Alkyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionates such as 2-hydroxyphenyl) propionate; 2,6-di-tert-butyl-α-dimethylamino-p-cresol, 2 , 2′-methylenebis (4-methyl-6-tert-butylphenol) (manufactured by Kawaguchi Chemical Co., Ltd .: Antage W-400), 2,2′-methylene 2,2′-methylenebis (4-alkyl-6-t-butylphenol) s such as s (4-ethyl-6-t-butylphenol) (manufactured by Kawaguchi Chemical Co., Ltd .: Antage W-500); 4,4′-butylidenebis (3-Methyl-6-t-butylphenol) (manufactured by Kawaguchi Chemical Co., Ltd .: Antage W-300), 4,4′-methylenebis (2,6-di-t-butylphenol) (manufactured by Shell Japan Co., Ltd .: Ionox 220AH) 4,4′-bis (2,6-di-t-butylphenol), 2,2- (di-p-hydroxyphenyl) propane (manufactured by Shell Japan, Inc .: bisphenol A), 2,2-bis (3 , 5-di-t-butyl-4-hydroxyphenyl) propane, 4,4′-cyclohexylidenebis (2,6-t-butylphenol), hexamethylene glycol bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] (manufactured by Ciba Specialty Chemicals: Irganox L109), triethylene glycol bis [3- (3-t-butyl-4- Hydroxy-5-methylphenyl) propionate] (manufactured by Yoshitomi Pharmaceutical: Tominox 917), 2,2′-thio- [diethyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] (Ciba Specialty Chemicals: Irganox L115), 3,9-bis {1,1-dimethyl-2- [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy] ethyl } 2,4,8,10-tetraoxaspiro [5,5] undecane (Sumitomo Chemical: Sumilizer GA80), 4,4 ′ Bisphenols such as thiobis (3-methyl-6-tert-butylphenol) (manufactured by Kawaguchi Chemical Co .: Antage RC), 2,2′-thiobis (4,6-di-tert-butyl-resorcin); tetrakis [methylene- 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane (manufactured by Ciba Specialty Chemicals: Irganox L101), 1,1,3-tris (2-methyl-4-hydroxy- 5-t-butylphenyl) butane (Yoshitomi Pharmaceutical Co., Ltd .: Yoshinox 930), 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene (Manufactured by Shell Japan: Ionox 330), bis- [3,3′-bis- (4′-hydroxy-3′-t-butylphenyl) butyrica Glycol ester, 2- (3 ′, 5′-di-tert-butyl-4-hydroxyphenyl) methyl-4- (2 ″, 4 ″ -di-tert-butyl-3 ″ -hydroxyphenyl) methyl Polyphenols such as -6-tert-butylphenol, 2,6-bis (2'-hydroxy-3'-tert-butyl-5'-methyl-benzyl) -4-methylphenol; pt-butylphenol and formaldehyde Examples include condensates and phenol aldehyde condensates such as a condensate of pt-butylphenol and acetaldehyde.

  Examples of phosphorus antioxidants include triaryl phosphites such as triphenyl phosphite and tricresyl phosphite, trialkyl phosphites such as trioctadecyl phosphite and tridecyl phosphite, and tridodecyl trithiophosphite. It is done.

  These antioxidants can be used alone or in combination within a range of 0.01 to 2.0 parts by weight with respect to 100 parts by weight of the base oil.

  Metal deactivators that can be used in combination with the compositions of the present invention include 4-alkyl-benzotriazoles such as benzotriazole, 4-methyl-benzotriazole, 4-ethyl-benzotriazole; 5-methyl-benzotriazole, 5- 5-alkyl-benzotriazoles such as ethyl-benzotriazole, 1-alkyl-benzotriazoles such as 1-dioctylaminomethyl-2,3-benzotriazole; 1 such as 1-dioctylaminomethyl-2,3-toltriazole Benzotriazole derivatives such as alkyl-tolutriazoles; 2- (alkyldithio) such as benzimidazole, 2- (octyldithio) -benzimidazole, 2- (decyldithio) -benzimidazole, 2- (dodecyldithio) -benzimidazole ) Benzimidazoles; benzimidazole derivatives such as 2- (alkyldithio) -toluimidazoles such as 2- (octyldithio) -toluimidazole, 2- (decyldithio) -toluimidazole, 2- (dodecyldithio) -toluimidazole; Indazole derivatives such as tolindazoles such as indazole, 4-alkyl-indazole, 5-alkyl-indazole; benzothiazole, 2-mercaptobenzothiazole derivative (manufactured by Chiyoda Chemical Co., Ltd .: Thiolite B-3100), 2- (hexyldithio) 2- (alkyldithio) benzothiazoles such as benzothiazole and 2- (octyldithio) benzothiazole; 2- (alkyldithio) such as 2- (hexyldithio) tolthiazole and 2- (octyldithio) tolthiazole Ruthiazoles; 2- (N, N-diethyldithiocarbamyl) benzothiazole, 2- (N, N-dibutyldithiocarbamyl) -benzothiazole, 2- (N, N-dihexyldithiocarbamyl) -benzothiazole, etc. 2- (N, N-dialkyldithiocarbamyl) benzothiazoles; 2- (N, N-diethyldithiocarbamyl) tolthiazole, 2- (N, N-dibutyldithiocarbamyl) tolthiazole, 2- (N , N-dihexyldithiocarbamyl) tolthiazole and other 2- (N, N-dialkyldithiocarbamyl) -tolzothiazoles and other benzothiazole derivatives; 2- (octyldithio) benzoxazole, 2- (decyldithio) benzo 2- (alkyl) such as oxazole, 2- (dodecyldithio) benzoxazole Dithio) -benzoxazoles; benzoxazole derivatives such as 2- (alkyldithio) toluxazoles such as 2- (octyldithio) toluxazole, 2- (decyldithio) toluazole and 2- (dodecyldithio) toluoxazole; 2 , 5-bis (heptyldithio) -1,3,4-thiadiazole, 2,5-bis (nonyldithio) -1,3,4-thiadiazole, 2,5-bis (dodecyldithio) -1,3,4-thiadiazole 2,5-bis (alkyldithio) -1,3,4-thiadiazoles such as 2,5-bis (octadecyldithio) -1,3,4-thiadiazole; 2,5-bis (N, N-diethyl) Dithiocarbamyl) -1,3,4-thiadiazole, 2,5-bis (N, N-dibutyldithiocarbamyl) -1,3 2,5-bis (N, N-dialkyldithiocarbamyl) -1,3,4, such as 4-thiadiazole, 2,5-bis (N, N-dioctyldithiocarbamyl) -1,3,4-thiadiazole -Thiadiazoles; 2-N, N-dibutyldithiocarbamyl-5-mercapto-1,3,4-thiadiazole, 2-N, N-dioctyldithiocarbamyl-5-mercapto-1,3,4-thiadiazole, etc. 2-N, N-dialkyldithiocarbamyl-5-mercapto-1,3,4-thiadiazoles and the like thiadiazole derivatives; 1-alkyl-2 such as 1-di-octylaminomethyl-2,4-triazole, And triazole derivatives such as 4-triazoles.

  These metal deactivators can be used alone or in combination within the range of 0.01 to 0.5 parts by weight with respect to 100 parts by weight of the base oil.

  Examples of the antifoaming agent include organosilicates such as dimethylpolysiloxane, diethyl silicate, and fluorosilicone, and non-silicone antifoaming agents such as polyalkyl acrylate. The addition amount can be used alone or in combination within a range of 0.0001 to 0.1 parts by weight with respect to 100 parts by weight of the base oil.

  As the viscosity index improver, for example, non-dispersed viscosity index improvers such as polymethacrylates, ethylene-propylene copolymers, olefin copolymers such as styrene-diene copolymers, etc., and nitrogen-containing monomers are copolymerized with these. And dispersion type viscosity index improvers. The addition amount can be used alone or in combination within a range of 0.05 to 20 parts by weight with respect to 100 parts by weight of the base oil.

  Examples of the pour point depressant include polymethacrylate polymers. The addition amount can be used in the range of 0.01 to 5 parts by weight with respect to 100 parts by weight of the base oil.

  Examples of the detergent dispersant include metal detergents such as neutral or basic alkaline earth metal sulfonate, alkaline earth metal phenate, alkaline earth metal salicylate, alkenyl succinimide, alkenyl succinate or boron thereof. Ashless dispersants such as modified products with compounds, sulfur compounds and the like. The addition amount can be used alone or in combination within a range of 0.01 to 1 part by weight with respect to 100 parts by weight of the base oil.

  As extreme pressure agents, sulfur-based extreme pressure agents such as dialkyl sulfide, dibenzyl sulfide, dialkyl polysulfide, dibenzyl disulfide, alkyl mercaptan, dibenzothiophene, 2,2′-dithiobis (benzothiazole); trialkyl phosphate, Phosphorus extreme pressure agents such as triaryl phosphate, trialkyl phosphonate, trialkyl phosphite, triaryl phosphite, dialkyl hydrogen phosphite; zinc dialkyldithiophosphate, dialkyldithiophosphate, trialkyldithiophosphate Phosphorus / sulfur extreme pressure agents such as esters, acidic thiophosphates, and trialkyltrithiophosphites can be used. These extreme pressure agents can be used alone or in combination within the range of 0.1 to 2 parts by weight with respect to 100 parts by weight of the base oil.

  Examples of demulsifiers include known ones that are commonly used as lubricating oil additives. The addition amount can be used in the range of 0.0005 to 0.5 parts by weight with respect to 100 parts by weight of the base oil.

  The lubricating oil composition of the present invention is suitable for lubrication of a site where the surface pressure of the sliding surface is 800 MPa to 2000 MPa. When a general lubricating oil is used, the oil film breaks and boundary lubrication occurs under such high surface pressure conditions, metal-metal contact occurs on the lubricating surface, the sliding surface wears, or the sliding surface This causes the occurrence of metal fatigue and, in turn, cracks and pitching. The lubricating oil composition of the present invention vitrifies under such a pressure range and has a viscosity of 100 ° C. or higher of 40000 Pa · s, and by increasing the viscosity of the lubricating oil, a firm oil film is formed on the sliding surface and Contact is suppressed, and wear and fatigue damage on the metal surface of the sliding portion can be greatly reduced.

  As described above, the lubricating oil composition of the present invention is suitable for lubricating a portion where the surface pressure of the sliding surface is 800 MPa to 2000 MPa. Therefore, the lubricating oil of the present invention includes, for example, engine oil (for gasoline, diesel, etc.), transmission oil [gear oil (for industrial use, for automobiles), automatic transmission oil (automatic transmission oil, toroidal CVT oil, belt CVT oil) )], Power steering oil, shock absorber oil, traction oil, bearing lubricating oil, and the like, and particularly preferably used as transmission (gear) lubricating oil and bearing lubricating oil.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited at all by an Example.

The following compounds were used in each example and comparative example:

  Each sample oil was prepared by adding the amount of the above-mentioned compounds shown in Table 1 below to a commercially available transmission oil (Toyota genuine ATF T4 (manufactured by TonenGeneral)), and thoroughly stirring and mixing each sample oil. Chemical dimethyl silicone oil (trade name: KF96L) was used, and the viscosity at 100 ° C. at 800 MPa of the additive compound used in each example is also shown in Table 1.

  About the sample oil of each said Example and a comparative example, abrasion and fatigue of the test piece at the time of using them as lubricating oil were evaluated.

Evaluation of wear resistance The wear characteristics were evaluated by the wear scar diameter of the ball after completion of the test using a ball-on-plate reciprocating sliding test under the following conditions.
Specimen: SUJ2 ball / SUJ2 plate operating conditions: Surface pressure = 500, 800, 1000, 1500, 2000 MPa
Speed = 0.5m / s
Temperature = 100 ° C
Time = 120 minutes

The results of the abrasion test are shown in Table 2 below.

  There is no significant difference between the example and the comparative example under a pressure of 500 MPa, but when compared with the sample oil of the comparative example when the sample oils of Examples 1 to 8 are used under a pressure of 800 MPa or more. It can be seen that the amount of wear can be greatly reduced. This is considered to be because the compound A or compound B added in the sample oils of Examples 1 to 8 was vitrified under a high pressure of 800 MPa or more, and a strong oil film was formed. Further, in Comparative Examples 2 and 3, the amount of compound A or compound B was small, and the vitrified oil film was not sufficiently formed, so it is considered that the amount of wear increased. Although not shown in the table, in the case of the sample oil to which 24% by volume of Compound A or Compound B is added, although there is an effect of reducing wear, the fluidity is remarkably lowered at a low temperature (for example, −40 ° C.) and lubrication is performed. It was not practical as an oil.

  In Comparative Examples 4 to 6, the amount of wear is larger than in the Examples, but this is because the added silicone oil has a viscosity at 100 ° C. at 800 MPa of 39000 Pa · s, and cannot form a firm oil film due to insufficient vitrification. It is thought that it was because of.

Evaluation of fatigue resistance The fatigue resistance test was evaluated by the time until the specimen was damaged using the Mori type rolling fatigue test.
Operating conditions: Surface pressure = 500, 800, 1000, 1500, 2000 MPa
Temperature = 100 ° C

The results of the fatigue resistance test are shown in Table 3 below.

  There is no significant difference between the example and the comparative example under a pressure of 500 MPa, but when compared with the sample oil of the comparative example when the sample oils of Examples 1 to 8 are used under a pressure of 800 MPa or more. As a result, the fatigue life could be greatly extended. This is considered to be because the compound A or compound B added in the sample oils of Examples 1 to 8 was vitrified under a high pressure of 800 MPa or more, and a strong oil film was formed. Further, in Comparative Examples 2 and 3, the amount of compound A or compound B added was small, and it was considered that the fatigue life was shortened because a vitrified oil film was not sufficiently formed. Although not shown in the table, in the case of sample oil to which 24% by volume of Compound A or Compound B is added, although there is an effect of improving fatigue resistance, fluidity is remarkably low at a low temperature (for example, −40 ° C.) It was not practical as a lubricating oil.

  In Comparative Examples 4 to 6, the fatigue resistance is inferior to that in Examples, but this is because the added silicone oil has a viscosity at 100 ° C. at 800 MPa of 39000 Pa · s, and can form a firm oil film with insufficient vitrification. It is thought that there was not.

  As described above, it has been shown that the lubricating oil composition of the present invention is excellent in wear resistance and fatigue resistance. Moreover, since the lubricating oil composition of the present invention can form a strong oil film, it not only suppresses initial fatigue damage, but also has an effect of suppressing crack progress and pitching.

  The lubricating oil composition of the present invention is useful as a lubricating oil for metal sliding surfaces (for example, gears and bearings) under a high load.

FIG. 1 is a diagram showing an example of pressure-viscosity characteristics of a compound used in the present invention.

Claims (5)

A lubricating oil composition containing 5 to 20% by volume of a compound having a viscosity at 100 ° C. of 1000 Pa · s or less under a pressure of 700 MPa or less and vitrified to 40000 Pa · s or more under a pressure of 800 MPa or more. The lubricating oil composition of claim 1, wherein the compound is a di (C _3-8 cycloalkyl) alkane. Said compound is of formula (I):

[Wherein, R ¹ is a C _1-6 alkylene group _optionally substituted by a linear or branched C _1-6 alkyl group, and R ² and R ³ are independently linear or branched C _{1 -6} selected from the group consisting of alkyl groups, phenyl groups and halogens. ]
The lubricating oil composition according to claim 1, which is a dicyclohexylalkane represented by the formula: The lubricating oil composition according to any one of claims 1 to 3, which is used for sliding surface lubrication having a contact surface pressure of 800 to 2000 MPa. The lubricating oil composition according to any one of claims 1 to 4, which is used for bearings or gears.

Images